1. Field of the Invention
The present invention relates to an ink discharge detecting method for an ink jet recording apparatus, and the ink jet recording apparatus.
2. Related Background Art
Conventionally, a variety of recording apparatuses for recording onto a recording medium such as a paper or OHP sheet have been proposed, and especially, an ink jet recording apparatus which directly jets the ink from a recording head onto a recording sheet, has gained wide acceptance as a recording apparatus having the advantages of low running costs and silent recording operation.
On the other hand, the method for detecting that the amount of ink has decreased in such an ink jet recording apparatus involves optically detecting a float moving up or down within an ink tank, or detecting the variation in resistance between electrodes provided within an ink tank.
However, the above conventional methods had a drawback that since a detecting member such as a float or electrodes was necessary within the ink tank, the detecting member had to be also exchanged integrally with the cartridge to be exchanged when the amount of ink within the ink tank decreased, for example, in the case of a disposable recording head of the cartridge type in which the recording head was formed integrally with the ink tank, so that costs and wastes increased.
Further, the above conventional methods involved detecting analogue variation of ink quantity which resulted from decreasing amount of ink within the ink tank, whereby if the detected result was below a preset threshold, the ink absence was detected, at which time the ink within the recording head was not completely absent in practice, with the result that the decrease in the amount of ink was detected while a slight amount of the ink was left within the ink tank. Accordingly, there was a problem that because the waste ink unusable for the recording was produced, the running costs increased. Also, there was a problem that the ink level within the ink tank shifted up or down, along with the movement of the ink tank, bringing about malfunctions.